Dash-pot



W. G RO E N DASH-POT May 27, 1958 Original Filed Jan. 14, 1953 INVENTOR:WILLEM GROEN BY ATT'YS 2,836,264 DAsn-Por Willem Groen, Chicago, 111.,assignor to (insrud Machine Works, inn, Niles, lit, a corporation ofIllinois Original application January 14, 1953, Serial No. 331,233,

now latent No. 2,745,320, dated May 15, 1956. Divided and thisapplication March 6, 1956, Serial No. 569,721

3 Claims. (Cl. 188-96) This invention relates to milling machines andthe like, and has particular reference to a dashpot for controllinghigh-speed routers and drills and other machine tools. This applicationis a division of my copending application, Serial Number 331,233, nowPatent No. 2,745,320, granted May 15, 1956.

The main objects of this invention are to provide a dashpot which isadapted selectively to control the rate of gravitational descent of amilling head such as is shown in the said copending application and toafford relatively free elevation of the milling head; to provide animproved mechanism of this kind wherein valve means are coaxiallydisposed within the piston of the dashpot to adjustably meter the flowof fluid through the piston and control the rate of movement of thepiston in one direction in the dashpot; to provide a movable check valvecoaxially within the piston and biased to close a central port andbranch ports in the piston whereby the piston is adapted to move in onedirection at a controlled rate and in the other direction substantiallyfree from resistance of fluid in said dashpot; to provide a coaxialbleed port in the check valve itself, without the necessity for separatevalve structure therefore; to provide a needle valve adjustably receivedin coaxial relation within a piston rod of said piston for controllingthe efiective diameter of said bleed port and the rate of fluid flowtherethrough when the piston is moved in one direction whereby tocontrol selectively the rate of movement of said piston in said onedirection; and to provide a dashpot having coaxially disposed annularcomponents, exceptional compactness, and relatively few parts, wherebyreduced costs of manufacture and greater efficiency and uniformity ofoperation are obtained.

Other objects and advantages of the invention will become apparent asthe description proceeds in accordance with a specific embodiment of theinvention as shown in the accompanying drawings, in which:

Fig. 1 is a vertical axial section of the improved dash- P Fig. 2 is avertical transverse section taken on line 22 of Fig. 1; and

Fig. 3 is a vertical transverse section taken on the line 33 of Fig. 1.

As set forth in my copending application, Serial Number 331,233, thedashpot of the invention is particularly adapted for use with theactuator mechanism disclosed in the said application for the purpose ofcontrolling the gravitational descent of the milling head therein shown,although it is by no means limited to such a use. In the said copendingapplication, the milling head is shown to be raised by a pneumatic jackwhich automatically retracts a piston rod with a fixed shoulder toactuate a bell crank to which the milling head is pivotally connected.The closing of a microswitch is effective to operate the pneumatic jackto move the piston rod in the other direction so as to release the bellcrank, and to permit the milling head to fall by force of gravity, by

virtue of a slidable connection between the respective bell crank armand the piston rod. By pivotally connecting an extension of the bellcrank to the piston of the dashpot of the present invention, the rate ofdescent of the milling head is adjustably reduced, due to the compactmetering means coaxially mounted in the dashpot piston. On the otherhand, when itis desired to elevate the milling head, the dashpot oiierssubstantially no resistance, since the check valve in which the meteringorifice or bleed port is formed will then move out of sealing engagementwith a relatively large central aperture in the dashpot piston andpermit substantially unrestricted flow of the cushioning fiuid throughthe piston.

Referring now to Fig. 1, the dashpot of the present invention comprisesa cylinder 32 attached to a suitable supporting structure, as by lateralgudgeons 33, and having a piston 40 slidably received therein withpiston rods 31 and 41 axially connected to opposite hub extensions 42and 42 of the piston. A head block is threadedly received on the pistonrod 31, and when the dashpot is utilized in the construction shown inthe aforesaid application Serial Number 331,233, the aforementioned bellcrank extension is pivotally connected directly thereto.

7 As shown in Figs. 1, 2 and 3, the dashpot cylinder 32 is closed atboth ends by heads 38 and 39, the piston rods 41 and 31 being slidablyreceived therethrough in suitably sealed relationship. The piston has amain port 43 forming a relatively large passage with branch passages 44and 44' communicating with the chamber 45 at the right side of thepiston. bored on the left side of the piston 40 to form a guideway for acheck valve 45 which is tapered to seat against and partly close theleft-hand end of the main port 43, and the valve 45' is biased andnormally urged against its seat by the spring 46. Branch ports 47 and47' extend radially through the hub walls at the left side of the seatnear the right-hand end of the valve 45'. A relatively small bleed port48 extends axially through the a valve 45 and its effective diameter iscontrolled by a needle valve 49 that extends through an axial bore inthe piston rod 31. An inlet port 48 in hub 42 affords access from thecylinder on the left-hand side of piston 44) to bleed port 43. The stem50 of the needle valve 49 is adjustably connected to the rod 31 bythreads 51, and has a knurled head 52 for adjusting the position of theneedle valve 49 axially of the rod 31.

The cylinder 32 is normally filled with oil and its heads 38 and 39 areprovided with ports 53 and 54 respectively, for injecting and removingthe liquid contents of the cylinder. The port 53 is closed by plug 55and the port 54 is closed by a valved oil cup 56.

The flow of liquid through the bleed passage 43 sets the speed at whichthe piston 49 can move in the left hand direction under the load that isbeing controlled.

This flow through the passage 48 is restricted by the needle 49, andthus can be adjusted to vary the speed of piston movement by turning theneedle forward or back by the knob 52.

As shown in Fig. 1, the dashpot 32 offers practically no resistance tomovement of piston 40 to the right since such movement causes the liquidto enter the passages 44 and 44' and force the valve 45' away from itsseat at the left-hand end of the passage 43, thus opening that passageto the radial ports 47 and 47 and permitting a rapid flow of liquidthrough the piston to the left hand side thereof. Consequent relativelyfree and rapid movement of the piston 46 to the right is obtained.

It is to be noted that in the use of this invention shown in my saidcopending application, the control of the down stroke speed of themilling head when operating as a The hub 42 is counterdrill avoids thebreaking of the drill when it comes through the work. Without suchcontrol a drill, on passing through the work and meeting lessresistance,

-' tends to shoot through while the chip is too strong to be cut easilywith the result that the'drill is often broken on? i The main advantagesof this invention reside in the siinplified'form, construction, andarrangement of the dash pot and its components whereby a very simple andfool proof assembly is had, thus minimizing cost of assemblv andassuring perfect, readily regulated operation. Other advantages residewherein all parts are of annular form and thus easily and cheaplymanufactured; and in the coaxial arrangement of the parts whereby .adashpot of very large load capacity is'had in a device of relativelysmall size.

. Although but onespecific embodiment of this invention is herein shownand described, it will be understood that details of the constructionshown may be altered or omitted without departing from the spiritof thisinvention as defined by the following claims.

I claim:

1. A dashpot comprising a cylinder, a fluid in said cylinder, a pistonslidably mounted in said cylinder and having a central porttherethrough, said piston having a coaxial cylindrical hub extensionon'eachside'thereof, one of said hub extensions having a cylindricalbore therein, a cylindrical check valve'slidably received in the bore ofsaid one hub extension and having a conical valving tip, said valvebeing coaxially' biasedinto seating V engagement with the adjacent endof said central port said one hub'extensionhavinglateralfbranchiports-leading from said central port to saidcylinderpsaid check 'valve" normally closing off communication. betweenQsaid central port and said branch ports, said check valve having ableed port extending co'axially therethrough, said one extension havingafclosur e for said here atits free end' and having a lateral inletpassage communicating with said bleed port at the end of thevalveopposite said tip, said central port normally communicating withthe cylinder through said bleed port and inlet passage, said pistonhaving a passage providing communicatio'nbetween said central port'andthe cylinder on the other side of said piston, and the other hubextension of said piston having an adjustable needle member extending 1axially therethrough and into said central port for regulating theeifective opening area of said check valvebleed port when said checkvalve isin seated position.

- 2. A dashpot comprising a cylinder, 21 fluid in said cylinder, apiston slidably mounted in said cylinder and having a centralport'opening axially therethrough, said piston having a cylindricalcoaxial hub extension on each side thereof, one of said hub extensionshavinga cylindrical bore leading to said centralport, a check valveslidably mounted coaxially in the bore of saidione hub extension andbiased into seating engagement with the adjacent end'of said centralport opening, said one extensionhaving lateral branch ports providingcommunication between said cylinder and said central port when saidcheckvalve is in opened unseated position, said in 'the construction side of,said, cylinder. andthrough said other extension into the central portopening of said piston andi'n axial alignment with the. bleedport ofsaid check valve, and. j

check valve having a cylindrical body terminating in a conical valvingtip and having a bleed port extending coaxially through the tip andbody, said one extension having a laterally directed passagecommunicating withthe bore thereof, said central port communicating withthe cylinder on the respective side of said piston through said bleedport and said inlet passage, said piston having a passage thereinproviding communication between said central port and the cylinder onthe other side of said piston, said piston including a piston rodsecured in coaxial relation to the end of the other of saidhubextensions and slidably received through the corresponding having acentral port opening axially therethrough, said piston having anintegral hub extension on each side thereof, one of said hub extensionshaving an. axial bore leading to said central port and an axiallymovable conical check valve slidably fitted in said bore and re-,

siliently biased into seating engagement with said 'central port, saidone extension having radial branch ports therein communicating. saidcylinderwith saidcentral port at the valve seat end of the central port,said. radial ports being closed to'said central port by said'check.valve when. said check valve is in seated position, said check valvehaving a coaxial bleed port therethrough and 'said'one extension havinga radial inlet passage com mu'nicating therewith, said central portnormally com-' municating with the cylinder on the respective sideofsai'd piston through said bleed port and inlet passage,jsaid' pistonhaving lateral passages therein providing communication between saidcentral port and the cylinder on the other side of said piston, saidpistonincluding a piston rod secured in coaxial relation tothe end ofeach of' said hub extensions and slidably received through thecorresponding end Wall of said cylinder, a needle valve 2 extendingcoaxially through the piston rod on saidother means for adjusting saidneedle valve axially and rela-. tive to saidcheck valve for varying theeffective area of said bleed port when said check valve is in seatedposition. References Cited in the file of this patent UNITED STATESPATENTS 1,455, 91

West May 15, 1923. 2,032,189 Stilling Feb. 25, '1936 2,315,531 Lucht'Apr." 6, 1943 2,559,047

check valve is in seated Porter et a1. July 3, 19:51 1

